Since when have 2 Slams ever been a stretch for Federer? He has been in 16 of the last 20 finals and 3 semis of the other 4. Even in a year plagued with illness, he still managed to make 3 Slam finals and a semi, winning 1 and almost 2. 2 Slams in a year is by no means a stretch for Federer. And what makes the AO out of reach? I think he's the favourite to win it, as I see him at 2 of the other 3 Slams.
As for the Grand Slam, it's unlikely, but not a totally ridiculous suggestion. I mean, he almost did it in 2006 and 2007. Was just one match away in each year.
I agree he has a decent chance to win in 3 of the Slams and he would have a great chance at RG if Nadal gets injured, etc. But there are also some things you have to consider:
His age is going to become a big factor from now. It´s really tough to mantain his level from 2004-07 both mentally and physically. Those are really high standards to mantain for more than 4-5 years especially in this era where the game is physically more demanding than ever.
He reached the semifinals at the AO but he was close to losing in the early rounds against Tipsarevic and his loss in the semifinals was in straight sets.
He reached the final at RG again but the final wasn´t competitive unlike in previous years and his game was far from convincing before the final.
He dominated at Wimbledon until the final and it´s true that it was a close 5 setter but you can´t deny that he won the 3rd and 4th sets by a hair in really close tie-breaks even saving matchpoint in the 4th. Out of 5 sets he played against Nadal he didn´t win one set convincingly.
Then he won the USO but he didn´t play so well before the final and he also had to play a 5 setter in the early rounds. And he didn´t win any Masters Series this year. So it´s true that he made the semifinals or better in all the Slams but I don´t feel he is a lock in the semifinals of every Slam after this year and the top players above/behind him are at least 5 years younger.
All these factors make me think that we will not see the Federer of 2004-07 again. This is not to bash Federer, it´s just the way I see it.